Rock drill tool, rock drill bit and production method

ABSTRACT

A rock drill tool, which comprises a rock drill bit as well as a drill rod detachably connected with the rock drill bit, where the joint between the rock drill bit and the drill rod is effected by means of a conical connection. The rock drill bit has a generally conical cavity, and the drill rod has a generally conical portion. The conical cavity is provided with a crest-shaped projection, which has a rectilinear extension along the envelope surface of the conical cavity, that the conical portion has a groove, which has a generally rectilinear extension along the envelope surface of the conical portion, and that the crest-shaped projection is received in the groove. A rock drill bit and a production method are also disclosed.

FIELD

The present disclosure relates to a rock drill tool comprising a rock drill bit and a drill rod detachably connected to the rock drill bit. The type of drilling that applies in the rock drill tool defined above is percussive and simultaneous rotary drilling. The disclosure also relates to a rock drill bit and a production method.

BACKGROUND

In the discussion of the background that follows, reference is made to certain structures and/or methods. However, the following references should not be construed as an admission that these structures and/or methods constitute prior art. Applicant expressly reserves the right to demonstrate that such structures and/or methods do not qualify as prior art.

A device for the detachable assembly of parts of rock or earth drills is previously known, wherein the drill rod and the drill bit are connected by means of a conical connection. Thus, the drill bit has a generally conical cavity while the end of the drill rod that should be received in the cavity is generally conical. The conical part of the drill rod is provided with a number of recesses/indentations, which preferably extend along the entire extension of the conical portion in the longitudinal direction of the drill rod. Said recesses/indentations promote the grip between the conical portions of the drill rod and drill bit. The recesses/indentations are produced by means of grinding, which is an expensive production method.

A drill bit is previously known that is provided with a generally conical cavity, in which a conical end of a drill rod is intended to be received. Preferably, the generally conical cavity defines three areas, which between themselves have countersinks extending in the longitudinal direction of the drill bit and having a depth of 50-100% of the width of an area. This makes the areas flexible so that they can adapt to irregularities of the drill rod, wherein said irregularities, for instance, may originate from the production.

A drill bit is previously known having a generally conical cavity, in which a conical end of a drill rod is intended to be received. The drill bit and the drill rod together form a rock drill tool. The conical cavity is provided with a plurality of grooves that extend in the longitudinal direction of the drill bit, the grooves being defined by a valley having peaks on both sides of the valley. The cone angle of the drill rod is somewhat greater than the cone angle of the cavity. When drilling is carried out using the known rock drill tool, a plastic deformation of the peaks takes place so that a greater contact surface is obtained. Thereby, the grip between the drill bit and the drill rod is improved.

SUMMARY

An object of the presently disclosed toll, bit and method is to provide a rock drill tool of the kind defined by way of introduction, wherein the joint between the drill rod and the drill bit should prevent a relative motion between the drill rod and the drill bit from taking place.

Another object of the presently disclosed tool, bit and method is that both the drill bit and the drill rod should be structurally simple and thereby also relatively inexpensive to produce.

At least some objects are realized by means of a rock drill tool and a drill bit having the features defined in the appended independent claims. Preferred embodiments of the invention are defined in the dependent claims.

An exemplary rock drill tool comprises a rock drill bit, and a drill rod detachably connected to the rock drill bit, the joint between the rock drill bit and the drill rod being effected by means of a conical connection, wherein the rock drill bit has an, at least partly, conical cavity, wherein the drill rod has a generally conical portion, the conical portion having a driver member that is positioned within an envelope surface of the conical portion, one end of said driver member situated closer to an end of the conical portion than is a second end of the driver member, wherein the conical cavity is provided with a projection, said driver member overlapping the projection, and wherein the projection is in the shape of a ridge.

An exemplary rock drill bit to be included in a conical connection, the rock drill bit comprising an, at least partly, conical cavity, the conical cavity being provided with a projection, an end of the projection being situated closer to a bottom of the cavity than is the other end of the projection, wherein the projection has a shape of a rectilinear ridge.

An exemplary method for the production of an, at least partly, conical cavity of a rock drill bit, which is intended to be included in a conical connection, comprises reaming by means of an end milling cutter at least a portion of the conical cavity, wherein a relative motion between the rock drill bit and the end milling cutter during reaming is around a first centre axis of the rock drill bit, and wherein the relative motion is 80-90% of a full revolution around the centre axis.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWING

Below, preferred embodiments of the invention will be described, reference being made to the accompanying drawings, wherein:

FIG. 1 shows an end view of a drill bit, which drill bit is included in a rock drill tool.

FIG. 2 shows a side view of the drill bit according to FIG. 1.

FIG. 3A shows a side view of the conical end of a drill.

FIG. 3B shows a side view of the drill rod according to FIG. 2, the drill rod being rotated by 90° so that the left side in FIG. 3A is facing the observer.

FIG. 3C shows an end view of the drill rod according to FIG. 3A, the conical part facing the observer.

FIG. 4 shows a perspective view of the drill rod according to FIG. 3A.

FIG. 5 shows a section, transverse to the longitudinal direction of the rock drill tool, through the drill bit and the drill rod when the drill rod is received in the drill bit.

FIG. 6 shows a section, transverse to the longitudinal direction of the rock drill tool, through the drill bit and the drill rod when an alternative embodiment of a drill rod is received in the drill bit.

FIG. 7 shows a section through a blank for the manufacture of an alternative drill bit.

FIG. 8 shows a section through a blank further machined in comparison with the blank shown in FIG. 7.

DETAILED DESCRIPTION

The drill bit 1 shown in FIGS. 1 and 2 comprises a sleeve-shaped part 3 as well as a bit part 5 integrated with the sleeve-shaped part. The sleeve-shaped part 3 has an internal cavity 7, which generally is conical, the cone being straight and circular. In the conical part thereof, the cavity 7 tapers from the open end thereof toward the bit part 5. The cavity 7 has an inner end that is smoothly rounded. This design is advantageous as for avoiding crack formation. The half cone angle of the conical cavity 7 is designated α1 in FIG. 2.

As is seen in FIG. 1, the cavity 7 does not have an entirely smooth envelope surface, but it comprises a projection or a driver member in the shape of, for example, a ridge/crest/tappet 9, which preferably is rectilinear and longitudinally directed in a plane that contains a first centre axis C1-C1 of the drill bit 1. The projection 9 has a height decreasing toward the bottom of the cavity 7, which is illustrated by the angle β defined by the projection 9 in relation to the first centre axis C1-C1 having a smaller value than the half cone angle α1 of the cavity 7.

The dashed circles drawn in FIG. 1 symbolize an end milling cutter P, which is used to produce the cavity 7. By not completing a full revolution with the end milling cutter P, the projection 9 is obtained inside the cavity 7. In the normal case, the mutual relative rotation between the end milling cutter and the drill bit 1 is in the interval of 310°-320°. This is an exceptionally easy way to produce the projection 9.

The drill rod 10 shown in FIGS. 3A-3C is provided with a conical portion 11 at one end thereof, said conical portion 11 defining a half cone angle α2 in relation to a second centre axis C2-C2 of the drill rod 10. In the envelope surface of the conical portion 11, a groove 12 is recessed, which has rectilinear side bordering edges 12A, that are situated in the envelope surface of the conical portion 11. Furthermore, the side bordering edges 12A are situated in planes that extend through or contain the second centre axis C2-C2 of the drill rod 10.

According to a preferred method of producing said groove, use is made also here of the end milling cutter by means of which the cavity 7 is produced. This end milling cutter is preferably an end-cutting end milling cutter. In doing so, the bottom of the groove 12 defines an angle α3 relative to C2-C2 that is less than the half cone angle α2 of the conical portion 11. As is most clearly seen in FIG. 3A, the groove 12 has at the portion 12A, i.e. apart from the portion 12B where the groove 12 goes into nothingness, a depth that is not constant but decreases toward the free end of the conical portion 11. In FIG. 3B it is seen that the width of the groove 12, apart from the portion 12B where the groove 12 goes into nothingness, also decreases toward the free end of the conical portion 11.

The half cone angle α1 of the cavity 7 has nominally the same value as half the cone angle α2 of the conical portion 11 of the drill rod 10. However, the cone angle α1 of the cavity 7 has a positive tolerance while half the cone angle α2 of the conical portion 11 has a negative tolerance. Normally, 5°<α1, α2<10° applies. The angle β is normally in the interval of 2°<β<8°, however, wherein β<α1 must hold. The angle α3 of the groove 12 is normally in the interval of 2°<α3<8°, however, wherein α3<α2 must hold.

In the cross section shown in FIG. 5 through the conical portion 11 and the sleeve-shaped part 3 of the drill bit 1, the contour of the groove 12 is shown in a certain position in relation to the projection 9, more precisely, the projection 9 is positioned in the middle of the groove 12, which generally has a concave cross-section. The projection 9 is defined by two portions that have concave cross-sections and meet in a tip. There is a gap δ between the extremity of the projection 9 and the bottom of the groove 12 in the position shown in FIG. 5. The reason therefore is that there is an aim to get a satisfactory surface contact between the conical cavity 7 of the drill bit 1 and the conical portion 11 of the drill rod 10. The smallest distance between the bottom of the groove 12 and the centre axis of the drill rod is depicted by x.

In FIG. 6, an alternative embodiment of the drill rod 110 is shown. In the embodiment shown in FIG. 6, a driver member 112 has the shape of a planar surface, which is arranged in the envelope surface of the conical portion 111 of the drill rod 110. In the embodiment shown FIG. 6, the drill bit 1 may have an identical design as in the embodiment according to FIGS. 1-2. For that reason, the same reference designations as in the embodiment according to FIGS. 1-2 have been used.

The planar surface 112 has rectilinear side bordering edges 112A that are situated in the envelope surface of the conical portion 111. Furthermore, the side bordering edges 112A are situated in planes that extend through the centre axis of the drill rod 110. The continuous-line position of the contour of the planar surface 112 is intended to symbolize the initial position, i.e., when the conical portion 11 is mounted in the cavity 7 of the drill bit 1. The arrow R symbolizes the direction of rotation of the rock drill tool. This entails that the drill rod 110 will rotate in relation to the drill bit 1 until the planar surface 112 has assumed the dashed-line position in FIG. 6, i.e., the projection 9 has come into abutment against the surface 112 in the area of one side edge of the surface 112. The co-operation of the projection 9 with the planar surface 112 will promote the driving of the drill bit 1 when the drill rod 110 rotates. Thus, the projection 9 and the planar surface 112 constitute co-operating driver members. The driver members shown in FIGS. 1-5, i.e., the projection 9 and the groove 12, co-operate in principally the same way. Generally, the driver member of the drill rod, e.g., groove 12 or planar surface 112, overlaps the projection 9 of the drill bit 1 in both axial and circumferential direction.

In FIG. 7, a blank 201′ for an additional alternative embodiment of a rock drill bit is shown and in FIG. 8 an alternative embodiment of a rock drill bit 201 is shown that is made from the blank 201′. The blank 201′ according to FIG. 7 has a sleeve-shaped part 203 as well as a bit part 205. The blank 201′ according to FIG. 7 for a rock drill bit is obtained after one production step, wherein parts of the internal cavity have been produced by internal turning. In the embodiment in question, it is a matter of an innermost circular-cylindrical part 207A having a rounded bottom, a truncated conical part 207B bordering on the circular-cylindrical part and an additional outer part 207C that also is truncated conical, however having substantially smaller axial length than the inner truncated conical part 207B. The blank 201′ according to FIG. 7 obtained in such a way is rotationally symmetrical in respect of a third centre axis C3-C3.

The blank 201′ according to FIG. 7 is further machined so that the drill bit 201 according to FIG. 8 is obtained. In doing so, the outermost conical part 207C is machined by an end milling cutter, a reaming of the same part generally taking place. However, the reaming is not effected a full revolution around the centre axis C-C, but the relative rotation between the blank and the end milling cutter is approx. 300°-340°. This generates a projection in the shape of a ridge/crest/tappet 209, which preferably has a diminishing height along its longitudinal direction wherein the height is diminishing in direction inwardly towards the bottom of the cavity. This is illustrated in FIG. 8 by the angle β1 that depicts the angle formed by the ridge 209 and the centre axis C3. As for the value of the angle β1, it is referred to what has been disclosed above, for example, in the description regarding the embodiment according to FIGS. 1-2.

The reaming cuts so much material that, apart from the projection 209, a continuous straight, circular conical part 207B, and 207C is obtained outside the circular-cylindrical part. The ridge 209 has a length that is less than half the length of the generatrix that defines the continuous conical part 207B, 207C. Half the cone angle of the conical part 207B, 207C is designated α1′, and it should be in the corresponding interval as has been stated above for α1 in connection with the embodiment according to FIGS. 1-2. The relation between α1′ and β1 shall be β1<α1′. As is evident from FIG. 8 the rock drill bit 201 is provided with buttons being received in the bit part 205.

The drill rod that is to co-operate with the rock drill bit according to FIG. 8 has a driver member, for instance a groove or a surface that has a length along the generatrix of the conical surface being at least equally great as the length of the projection 209. However, the groove may be substantially longer than the length of the projection 209, wherein, for instance, the drill rod 10 shown in FIGS. 3-4 may be used together with the drill bit produced from the blank according to FIG. 8. Also here, it generally applies that the driver member of the drill rod overlaps the projection 209 in both axial and circumferential direction.

In the embodiments of a drill bit and a drill rod described herein, the cavity 7, 207 of the drill bit 1, 201 is provided with a single projection 9, 209, while the drill rod 10, 110 is provided with a single driver member in the shape of a groove 12 or a surface 112. However, within the scope of the present invention, it is conceivable that the cavity is provided with more projections, which preferably are arranged at a constant pitch along the circumference of the cavity, and that the drill rod has at least the corresponding number of driver members in the shape of grooves/surfaces, which overlap the projections when the drill rod is received in the drill bit.

At the described embodiment according to FIGS. 7 and 8 of a rock drill bit, a continuous conical surface 207B, 207C is obtained after forming of the projection 209 by milling the cavity end being situated closest to the opening. Within the scope of the present invention it is conceivable that a continuous conical surface is not formed but the conical part 207C, that is milled in connection with the making of the projection 209, connects via a shoulder having the same cone angle as the conical part 207B or that the conical part 207C has a slightly greater cone angle than the conical part 207B.

The groove 12 at the above-described embodiment of the drill rod 10 extends from the end of the conical part 11 and ends in nothingness before the conical portion 11 connects to the rest of the drill rod. Within the scope of the present invention it is conceivable that the groove/driver member extends all the way to the part of the drill rod having full diameter. It is also possible that the groove/driver member does not extend all the way to the end of the conical portion.

The ridge/crest/tappet 9 is rectilinear in the above-described embodiments. Within the scope of the present invention it is conceivable that the ridge/crest/tappet for example extends like a helix along the cavity of the rock drill bit, and therefore also the groove/the planar surface extends like a helix along the conical portion of the drill rod such that there will be an overlap at the groove/the surface and the ridge/crest/tappet.

Although described in connection with preferred embodiments thereof, it will be appreciated by those skilled in the art that additions, deletions, modifications, and substitutions not specifically described may be made without department from the spirit and scope of the invention as defined in the appended claims. 

1. A rock drill tool, comprising: a rock drill bit; and a drill rod detachably connected to the rock drill bit, the joint between the rock drill bit and the drill rod being effected by means of a conical connection, wherein the rock drill bit has an, at least partly, conical cavity, wherein the drill rod has a generally conical portion, the conical portion having a driver member that is positioned within an envelope surface of the conical portion, one end of said driver member situated closer to an end of the conical portion than is a second end of the driver member, wherein the conical cavity is provided with a projection, said driver member overlapping the projection, and wherein the projection is in the shape of a ridge.
 2. The rock drill tool according to claim 1, wherein the driver member has rectilinear first side bordering edges, and the first side bordering edges are situated in planes extending through a second centre axis of the drill rod.
 3. The rock drill tool according to claim 1, wherein the radially inner part of the projection is rectilinear, and the radially inner part lies in a plane that extends through a first centre axis of the rock drill bit.
 4. The rock drill tool according to claim 1, wherein the projection has a length that constitutes a major part of the length of the generatrix that defines the conical part of the cavity.
 5. The rock drill tool according to claim 1, wherein the projection has a length that is less than half of the length of the generatrix that defines the conical part of the cavity.
 6. A rock drill bit to be included in a conical connection, the rock drill bit comprising an, at least partly, conical cavity, the conical cavity being provided with a projection, an end of the projection being situated closer to a bottom of the cavity than is the other end of the projection, wherein the projection has a shape of a rectilinear ridge.
 7. The rock drill bit according to claim 6, wherein a radially inner part is rectilinear, and wherein the radially inner part lies in a plane that extends through a first centre axis of the rock drill bit.
 8. The rock drill bit according to claim 6, wherein the projection has a length that represents a major part of the length of the generatrix that defines the conical part of the cavity.
 9. The rock drill bit according to claim 6, wherein the projection has a length that is less than half of the length of the generatrix that defines the conical part of the cavity.
 10. A method for the production of an, at least partly, conical cavity of a rock drill bit, which is intended to be included in a conical connection, the method comprising: reaming by means of an end milling cutter at least a portion of the conical cavity, wherein a relative motion between the rock drill bit and the end milling cutter during reaming is around a first centre axis of the rock drill bit, and wherein the relative motion is 80-90% of a full revolution around the centre axis. 